
   A43P26161 
PRELIMINARY  (July, 2005, Version 1.1) 
13 
AMIC Technology, Corp.
All Banks Precharge 
All banks can be precharged at the same time by using 
Precharge all command. Asserting low on 
CS
 ,
RAS
 and 
WE
  with high on A10/AP after both banks have satisfied 
t
RAS
(min) requirement, performs precharge on all banks. At 
the end of tRP after performing precharge all, all banks are 
in idle state. 
Auto Refresh 
The storage cells of SDRAM need to be refreshed every 
64ms to maintain data. An auto refresh cycle accomplishes 
refresh of a single row of storage cells. The internal counter 
increments automatically on every auto refresh cycle to 
refresh all the rows. An auto refresh command is issued by 
asserting low on 
CS
 ,
RAS
 and 
CAS
 with high on CKE 
and 
WE
 . The auto refresh command can only be asserted 
with all banks being in idle state and the device is not in 
power down mode (CKE is high in the previous cycle). The 
time required to complete the auto refresh operation is 
specified by “t
RC
(min)”. The minimum number of clock cycles 
required can be calculated by dividing “t
RC
” with clock cycle 
time and then rounding up to the next higher integer. The 
auto refresh command must be followed by NOP’s until the 
auto refresh operation is completed. All banks will be in the 
idle state at the end of auto refresh operation. The auto 
refresh is the preferred refresh mode when the SDRAM is 
being used for normal data transactions. The auto refresh 
cycle can be performed once in 15.6us or a burst of 4096 
auto refresh cycles once in 64ms. 
Self Refresh 
The self refresh is another refresh mode available in the 
SDRAM. The self refresh is the preferred refresh mode for 
data retention and low power operation of SDRAM. In self 
refresh mode, the SDRAM disables the internal clock and all 
the input buffers except CKE. The refresh addressing and 
timing is internally generated to reduce power consumption. 
The self refresh mode is entered from all banks idle state by 
asserting low on 
CS
 ,
RAS
 ,
CAS
 and CKE with high on 
WE
. Once the self refresh mode is entered, only CKE state 
being low matters, all the other inputs including clock are 
ignored to remain in the self refresh.  
The self refresh is exited by restarting the external clock and 
then asserting high on CKE. This must be followed by NOP’s 
for a minimum time of “t
RC
” before the SDRAM reaches idle 
state to begin normal operation. If the system uses burst 
auto refresh during normal operation, it is recommended to 
used burst 4096 auto refresh cycles immediately after exiting 
self refresh. 
Deep Power Down Mode  
The Deep Power Down Mode is an unique function on Low 
Power SDRAMs with very low standby currents. All internal 
voltage generators inside the Low Power SDRAMs are 
stopped and all memory data will be lost in this mode. To 
enter the Deep Power Down Mode all banks must be 
precharged and the necessary Precharged Delay t
RP
 must 
occur.